Sounds like a great design, one I recommend.
You can put the HC on the outside instead of between the rafters:
https://www.backyardchickens.com/articles/aarts-coop-page.65912/
https://www.backyardchickens.com/attachments/coop-eaves-2-jpg.1353557/
How many hens will you have?
Where in this world are you located?
Climate, and time of year, is almost always a factor.
Please add your general geographical location to your profile.
It's easy to do, and then it's always there!